The screenshots show this prefab in an example map, that is NOT part of this file.
This prefab should be installed to sourcesdk\bin\orangebox\bin\TF2 Prefabs.
This is a prefab for single intel CTF maps, it contains a set of team filters, a logic_auto, and some trigger brushes.
On the beginning of map, the flag switches from Any to Blue to Red back to Any, this activates the directional arrows used by the CTF gamemode. When no player has the flag, it is set to any. Grey arrows point out the flag to all players. When a player picks up this flag, the brushes determine what team he is on, and set the flag opposite to this data. The opposing team sees their arrow pointing to the flag carrier. On dropping, capturing or returning, the flag resets to Any.
I have included an extra brush called trigger_notify, this is if you want the flag carrier to receive a message upon picking up the flag. Add a game_text entity and set it up so trigging trigger_notify displays the message.
This prefab works with a standard func_capturezone entity.